1. Field of the Invention
The present invention relates to a liquid crystal display device and a method of driving the same, and more particularly, to a dot inversion-type liquid crystal display device and a method of driving the same.
2. Description of the Related Art
Generally, liquid crystal display (LCD) devices control optical transmittance of liquid crystals using an electrical field so as to display images. The LCD device includes a liquid crystal panel in which a plurality of pixels each having a liquid crystal capacitor are arranged in a matrix, and a driving circuit for driving the liquid crystal panel.
The LCD devices are typically driven by an inversion method to prevent degradation of liquid crystals and improve the quality of images being displayed. The inversion method includes a frame inversion method, a dot inversion method, a line inversion method, etc.
In the frame inversion method, the polarities of the voltage applied to the liquid crystal molecules between a common electrode and a pixel electrode are repeatedly reversed frame by frame.
When a positive data voltage is applied in an even frame, a negative data voltage is applied in an odd frame.
While the frame inversion method consumes a small amount of power during switching, it is sensitive to a flicker phenomenon caused by asymmetric transmittances of positive and negative polarities and is vulnerable to crosstalk caused by interference between data.
In the line inversion method that is generally and widely applied in low resolution display devices such as VGA and SVGA displays, a data voltage is applied such that the voltage polarities of the pixels are changed in units of horizontal lines, line by line.
When a positive data voltage is applied to an odd line, and a negative data voltage is applied to an even line, in a next frame, opposite polarities of voltages are applied.
The line inversion method experiences less flicker phenomenon as compared with the frame inversion method since data voltages applied to adjacent lines have opposite polarities to one another. Further, voltages having opposite polarities are applied in a vertical direction, so that a coupling phenomenon occurring between data is compensated for, and little vertical crosstalk occurs as compared with the frame inversion method.
However, in a horizontal direction, voltages having the same polarity are applied, so that horizontal crosstalk occurs, and the number of switching cycle is increased compared with the frame inversion method, thereby increasing power consumption.
In the dot inversion method, data voltages having opposite polarities are applied between adjacent pixels in all directions (i.e., up/down and right/left). When a positive data voltage is applied to one of a plurality of pixels, a negative data voltage is applied to an adjacent pixel, and in the next frame, voltages having polarities opposite to the voltage polarities of the previous frame are applied.
The dot inversion method provides a higher quality image in comparison to other inversion methods, by compensating for the flicker phenomenon occurring between adjacent pixels in vertical and horizontal directions.
For this reason, among all polarity inversion methods, the dot inversion method can display the highest quality image and thus is widely applied to high resolution display devices such as XGA, SXGA and UXGA displays. However, the dot inversion method consumes larger amount of power compared to other inversion methods.
In the line inversion method, a polarity of a data signal Sd is inverted in every cycle, and a polarity of common voltage Vcom corresponding thereto is also inverted. Accordingly, in the line inversion method, since a polarity of the common voltage Vcom is inverted to correspond to the data signal Sd, a potential difference of 2Vd between the common voltage Vcom and the data signal Sd can be made even when a data voltage of Vd is applied.
In the dot inversion method, a polarity of the data signal Sd is inverted in every cycle with respect to a common voltage Vcom that is fixed. Accordingly, in the dot inversion method, when a data voltage of 2Vd is applied, a potential difference of 2Vd between the common voltage Vcom and the data signal Sd can be made. Here, the power consumption p is cv^2f, which is four times higher than that in the line inversion method.